1. Field of the Invention
The present invention relates to a motor, and in particular, to a motor including a brush for power supply.
2. Description of the Related Art
DC motors (hereinafter, also simply referred to as “motors”) are used in a wide variety of fields and applications ranging from electrical equipment for automobiles, etc., audiovisual equipment, and household electrical appliances to toys and models. A DC motor generally supplies an electric current to rotor winding from a DC power supply via a brush and a commutator that the brush slidably contacts.
The brush is housed and held in a brush holder in which a moving space is provided in a direction perpendicular to the rotating shaft of the commutator, so that the tip of the brush presses the commutator by the rear end portion thereof being biased with a biasing member. It is designed to provide a certain clearance between the brush and the holder, in view of the thermal expansion of each member and the dimensional accuracy of each component. Accordingly, when the commutator starts rotating, the brush may shake in a direction in which the commutator rotates by the frictional force with the commutator.
In order to suppress such looseness of the brush, a motor including a brush device has been devised, in which a pressing piece for pressing the brush toward a side wall of the internal walls of the brush holder, the side wall being on the side of the commutator rotating direction, is provided in the brush (see Japanese Patent Application Publication No. 2002-369457).
The aforementioned brush holder is made of a resin and a cut-out portion (notch) is formed. The pressing part is a member that is made by bending a metal material and has a spring property, and is fixed to the tip of a place of the brush holder, in the place the cut-out portion of the brush holder being formed. In the aforementioned brush device, it is aimed to suppress the looseness of the brush by pressing the brush onto one side wall of the brush holder with a metal material having a spring property. However, there is a limit in suppressing the looseness of the brush by the spring property of a metal material, and hence the looseness of the brush is caused due to the clearance between the brush and the brush holder.
In addition, a brush holder of another type is formed by bending a metal material. Even in such a type, however, there is a limit on the working accuracy of the bending, and a relatively large clearance is caused between the brush and the brush holder, thereby causing the looseness of the brush.